Lilmike's Cinema F-20 - Page 45

The DVC might be the cheapest replacement, but may not be the best. I know several people who have built the F20 with the RSS390HF-4 and are very satisfied. Without side by side real world measurements, it is really hard to say which is "better". On paper? You decide.

Dayton Audio RSS390HF-4 Reference HF @ $172.69
Power handling: 500 watts RMS (800 watts max)
Impedance: 4 ohms
Frequency range: 18 - 800 Hz • Fs: 18 Hz
Magnet weight: 150 oz.
SPL: 90 dB 2.83 V/1m, 87 dB 1W/1m
Xmax: 14mm

Dayton Audio DVC385-88 DVC @ $139.85
Power handling: 350 watts RMS/per coil (600 watts total)
Impedance: 8 ohm per coil / 4 ohm total
Frequency range: 20-450 Hz
Magnet weight: 112 oz
Frequency range: 19 Hz • SPL: 90 dB 1W/1m
Xmax: 15.1mm

i just went back and checked hornresp. the mfw, 390hf, and dvc385 all work quite similarly in the f20. the dvc has a smidgen less ripple in the frequency response, but the hf has that nice low inductance.

What if one was using them as reinforcement to a pair of front firing f20s, all so would you want to face the mouth towards the other mouths of the front firing f20s or would you face them towards the back. Or would it kind of be kind of like try it and find out. I just don't want any muddy sounds.

Then one would want to make sure he had the ability to adjust the phase/delay of the riser'd f-20's to blend well with the front ones. I will say, you better be ready to build some steps, that is a pretty big single step-up. your second row will TOWER above the first. haha

@duder ...

How big is your room? I built four F20s and I have to say (while I LOVE them)...it might have been just a tad overkill, even for the 25,000 cubic ft space in our dinner theater. Two probably would have been enough, but I would rather run 4 @ 65% capacity than 2 @ 100% capacity. I had to adjust my AVR to -12dB and only turn my amps up to about 65% - 75% depending on the source content with my AVR volume at 85%. Granted...I have not done any true EQ yet, but just a little bit of playing around shows me that the place would probably shake apart if I put everything to their RMS rated max SPL. Just say'n ... do you really NEED two more?

Maybe I wil start with 2 and see what happens, I have plenty of time to play around with subs on this since the room isn't done yet.

Dont remember where in the thread was the other horned sub you made lilmike. It was similar to the F20 but extended lower I think and was bigger. I just wanted to know how that subwoofer turned out.

spend the extra $33 and get the RSS390HF-4. I finally painted mine this weekend..

Did plans ever get posted for the "lilwrecker" that radman12 has?

If Mike doesn't have them up online - I can email them to you. I have the model, (Google Sketchup 3d, and HR). I might have a cultist also, I'll look. Shoot me a PM with your email..

is the lilwrecker the 15in cvx horn you guys were working on?

Dang Thad, you beat my record on longest unpainted f-20!! haha IIRC we werent too far apart in some of the first builds of these guys. Mine are long gone (to another fellow AVS'er) but I miss them every single day for that tremendous output...truly the best bang for the buck, until you start chasing single digits...

hehe, i was going on 7 months. wife didn't seem to mind so much and so it wasn't really a priority while we were birthing and learning to raise our first kid. I'm getting back into house projects now and it seemed prudent that I finish this one up. Single digits certainly don't interest me at this point - this thing suits all of my needs and plenty of my wants. anyone who builds one and sells/gives away should be flogged. :P

To quote the venerable Roy D Mercer, "HOW BIG A BOY ARE YA?"

I have received tentative wife approval for building a lilwrecker. I have a couple of projects to first finish up so I can clear out my basement. Once that is done, I can get started on this and I will start a build thread for when I do. It has been a long time since I tried to build a speaker cabinet so I'll share all of my fail as I go along.

I was told I could build two and put them anywhere I wanted because single guys have more freedom to do that kind of thing. So I guess I'll just be building one.

LilWrecker project just got put on hold.

I needed a new car and somehow convinced my wife that an Audi S4 was what we needed.

It does have a Bang & Olufsen audio system ... that's got to count for something, right?


Untitled by chilort, on Flickr

In addition, the general area where I wanted to put the horn has now been allocated for bookshelves.

How much would a crawlspace install attenuate the LilWrecker? The low frequencies should carry, right?

ported to the room or just hoping the sound travels through the floor? Big difference there...

Hoping it travels w/o cutting a hole. My RF-7s play low already so I need 80Hz on down I think. And I can hear the trunk subs of the cars that pass along the freeway. Kind of joking ... but kind of not joking.

eh, you are going to get a LOT more gain with having the sub port to in the room. My main suggestion though would be to move the sub around in the media room, where you MIGHT be able to do this, and see where it sounds the best, then decide if you can cut a hole to port it. from 80down youll lose a little of the upper frequencies I would think, as the frequencies get lower, the more omnidirectional the sound gets, and the less you should be affected. at least down to the tuning point of the f-20. It is worth a shot, just be prepared to make some other sacrifice before you are done so that beast will port or even fit in the room. Works great for a bench/coffee table if finished right!

I read through this thread again and many other F-20 threads.
My f-20 is in a rather small room for the output it has.
I have been thinking of seeing how I feel about some distortion below 20hz for some output below 20hz.
Currently I am using a BASH 300 with default resistors which gives me a high pass of 17.7.
The output I get at 18hz is reference and thd is only ~5%.

Anyone using an F-20 with a high pass lower than 17?
Any measurments with THD and room size.

From what I understand there isn't any more of a concern below 20hz as there is at 20hz from a driver standpoint.

If it was as simple as changing an miniDSP I would test my room myself. But due to having to change out resistors I want a little more data beforehand.
Edited by Shinyav - 9/18/12 at 1:16pm

I use dual THTs (more alike than different from F20) with boost below the 22Hz tuning, I get response down to 15-16Hz. I measure carefully to ensure that I am always within safe bounds.

JSS

What exactly do you measure for?

Alright I did a little more reading and am getting slightly further..

With the current values, using a second order high pass calc it seems like i get a roll off of
-1@16hz
-3@14hz
-5.5@12hz
-9@10hz
with a ~1db boost between 20hz and 40hz.

I am trying to figure out if there would be any potentially better Fc and Q for the amp paired with this sub.
My one stipulation is I can't trust myself to now really push the driver.
Is there any room for improvement with that fact?

I saw that mentioned quite a few pages back.
With my amp I can only seem to get rather wide boosts. This seems like if I am also boosting things above 20 as well.
I can get results like these
-3@10hz
+1@12hz
+3@14hz
+3.5@16hz
+3@18hz
+3@20
+2.5@22
+2@24
etc

Or something like

0@10
1@12
1.2@14
1.2@16
1@18
.9@20
Very little boost but basically no high pass.

Any input would be great, need to know what to think about from here.

edit: couple more questions.

With the reference HF having a 500watt RMS, is it better protected or even immune from thermal problems from a 300 watt amp,
The other safety concern is excursion, however, is it even possible to meet that problem on this driver under 19hz with only 300 watts?

If anyone has the inputs for hornresp to enter so I can model it myself that would be great. Still a bit confused on some things for it when setting it up specifically for this sub and with the reference HF

Thanks
Edited by Shinyav - 9/20/12 at 10:02am

All you are doing by trying to boost below the corner of 20hz on this horn is multiplying the THD by a rediculous amount. the F-20 has a corner of 20hz for a reason, yes there is response below that, and by all means use it, but bottom line is trying to get more out of this cabinet below it's corner is going to screw up the benefit of a horn in the first place: Higher efficiency and low distortion. a high pass for this cab is not only recommended by Mike, he almost will say it is necessary. If you want REAL sub 20hz content, you're going to have to go elsewhere...

Correct. I boost and test, knowing I never run anywhere near limits, REW can measure distortion very well, esp the new Beta version.

JSS

I had the understanding that the distortion produced depends on the driver producing them to begin with. I have read this entire thread quite a few times. I fully appreciate Lilmikes reasons for the 20hz highpass and respect it completely. This has just been stewing in my head due to things I have read about this horn and the THT with lower than tuning highpasses. I am just trying to learn and experiment with things I already have. I don't REALLY want sub 20hz.. just kinda want to mess around.

I have the gear to measure and have experimented with measuring THD and such. As I said above I just want to learn and mess around. I guess one of my questions would be what exactly is the problem that comes into play. I understand that the harmonics will be within band and be amplified by the horn and the frequencies below band will not be. However, as suggested with a low distortion driver it is possible to get some output without much in the way of harmonics. What is the danger then to the driver at those lower frequencies with boost. Does the boosted input with less output lead to overexcursion if not careful? I originally had thought that with a sealed box(like the back chamber) the lower the frequency the less excursion and more power needed.


By the way I don't mean to sound hardheaded or anything. I really appreciate all the input you guys have added to this thread and many others and have read most of both of yours posts. I really really enjoy my f-20 and lilmike was beyond helpful to me more than I can explain. I just really want to understand more and play around with things simply because I enjoy it.

I am using my horns outside their passband, to get more extension. There is only so much you can get with boost outside the passband without it sounding terrible because of distortion. The F20 has a small enough rear chamber that it controls excursion to a point, but you can run into overexcursion, but you will see distortion creep in prior. Hence, measuring with high level material. I use soho54's Audio Test DVD, the -0.5dB LFE tones. I do realize that the subwoofer can be called upon to produce an extra 6-8dB over what is just on the sub, if for any reason, a strong bass signal is in all channels (rare, but possible), so I give myself some leeway.

A folded horn is the best bang for buck way to get into high spl playback if you have some woodworking skills. The F20 is an improvement over the standard 3'x3'x2' THT in my opinion because of the fact that it can be used with the Reference HF driver standing up or lying down, due to driver orientation.

JSS